Shuttle crew completes Solar Max repairs; is Landsat-4 next?

April 12, 1984

By Robert C. CowenStaff writer of The Christian Science Monitor

Houston

Challenger astronauts have delivered ''the beef.'' Compressing what was originally scheduled as two work sessions into one, they have repaired the ailing Solar Maximum Mission observatory. If the satellite is successfully relaunched today as planned, it will give credibility to Frank Cepollina's vision of a new space era.

Mr. Cepollina, manager of the Solar Max repair project, has been proclaiming with the vigor of an Old Testament prophet that ''the era of the throwaway spacecraft has come to an end.'' From now on, he says, space scientists can design their equipment knowing it can be reburbished on orbit. No longer need they abandon a malfunctioning satellite. Furthermore, he foresees orbiting space factories where special materials or pharmaceuticals are made, taking advantage of a weightless environment. These, too, could be regularly serviced by visiting astronauts.

''There is some beef in this program,'' Cepollina says - a claim that this so-far successful mission has begun to substantiate.

Solar Max controllers at the Goddard Space Flight Center in Greenbelt, Md., were running a methodical check on the observatory at this writing. If everything works well, they expect that the astronauts will have used the shuttle's arm to lift the rejuvenated Solar Max out of the cargo bay at about 4: 28 a.m. Eastern standard time today. So far, the check-out has proceeded smoothly.

Astronauts George (Pinky) Nelson and James (Ox) van Hoften had emerged into the shuttle bay shortly before 4 a.m. yesterday. Working with efficiency and precision, they made the demanding repair operation look as easy as changing a tire on a car.

By 5:23 a.m., they had installed a baffle on an X-ray dector and replaced the observatory's attitude control module. The old module had blown three fuses by the 10th month after Solar Max was launched Feb. 14, 1980. The observatory should regain its capacity for precision pointing now that the failed module has been replaced. The astronauts then replaced the main electronics box for an instrument called a Chronograph/Polarimeter.

In all, according to Goddard controllers, the repair operation took about 3 hours, 45 minutes. That was far better than the 5 hours, 20 minutes that the controllers had estimated the job would take. This gave ''Pinky'' Nelson and ''Ox'' van Hoften extra time to check over the observatory, take photographs, and do an another engineering test of one of the manned maneuvering units (MMUs) with which astronauts fly freely in space.

At one point, Nelson inspected the observatory's trunion pin and made detailed measurements of it. He may have found the reason his trunion pin attachment device (TPAD) was unable to latch on to that fitting last Sunday. There is a small button close to the satellite's trunion pin. It is one of a number of such buttons that fasten down a thermal blanket. This button could have interferred with the TPAD as it seems to protude farther than the TPAD's designers had expected.

Thus mission officials now can claim that the astronauts have demonstrated the feasibility of having an MMU-equipped astronaut move to a satellite and dock with it. There seems little doubt that the maneuver would have been completed Sunday if that protruding button had been included in the game plan.

One nonessential aspect of the Solar Max rescue plan has had to be dropped, however. Challenger will not have enough orbital maneuvering propellant to boost the observatory to a 15-mile-higher orbit when it is released. As with all satellite orbits near Earth, that of Solar Max had gradually decayed due to a slight drag from the outer finges of the atmosphere. The observatory was slowly dropping to lower altitude orbits. The 15 mile boost would have added six months to Solar Max's estimate orbital life. But, since the observatory now is expected to function until early in the next decade, that additional six months would have been only a minor bonus, according to Mr. Cepollina.

However, orbital reboost will be more important for some future satellites, such as the Space Telescope. Cepollina explains that he and other Goddard experts would like at least to measure certain technical aspects of the effects on a satellite of a reboost operation. Thus mission officials were considering having Challenger give Solar Max a modest two-mile lift.

With what appears to be a successful satellite repair in hand, National Aeronautics and Space Administration officials now are looking forward to other possible satellite rescues. The ailing Landsat-4 is being studied. This is in a polar orbit. Its rescue must wait until the Air Force shuttle launch facility is ready at Vandenburg Air Force Base in California - the only pad from which a polar orbit can be reached.